The capacity for coordinated action is the foundation of much of humanity's greatest social and cultural achievements. Yet there are conditions under which cooperative behaviors do more harm than good, within and between groups. We review current research from a variety of social science disciplines exploring the oft-unquestioned ironic effects of cooperative behavior and conversely, the value of social conflict for positive outcomes – e.g., increased creativity and moral behavior, and concrete social change and equity. Recent reviews of prejudice reduction interventions have shed light on the hazards of exclusively promoting positive attitudes and emotions within and between groups. In complement, we focus on cooperative and conflictual behavior and the consequences thereof. To highlight issues researchers and practitioners should consider when developing social interventions, we summarize some of the common ironic effects of cooperative and conflict behaviors. Cooperative behaviors are socially and economically beneficial across a large variety of contexts; however, universal prescriptions for such behaviors may have unintended negative effects, whereas conflict is often requisite for promoting progress.